Description: The objective of this work is to identify the environmental chemicals in the Aberjona watershed that present human health hazards, to identify the environmental pathways of these chemicals, and to quantify past, present, and future human exposure to these chemicals. The plan of research is both field and laboratory oriented, and includes hydrologic processes responsible for chemical transport, chemical processes that control chemical toxicity and mobility, and close interaction with a program of human studies. Research will focus on: a)processes leading to human exposure to toxic chemicals via drinking water pumped from municipal Wells G and H in Woburn between 1964 and 1979; b)quantification of chronic and episodic release of toxic metals, especially arsenic, chromium, and mercury, from sediments into the heavily-utilized surface waters of the watershed; and c)quantification of primary environmental fate and human exposure processes, including biodegradation and movement of soil vapor, of anthropogenic organic chemicals on the watershed. Contribution to public education and outreach to the community of the Aberjona watershed will also continue to be goals of this work.